Multi-Material Thermal Barrier Coating System

ABSTRACT

The thermal barrier coating system comprises a matrix of a first chemistry with multiple embedded second phases of a second chemistry. The matrix comprises a stabilized zirconia. The second regions comprise at least 40 mole percent of oxides having the formula Ln 2 O 3 , where Ln is selected from the lanthanides La through Lu, Y, Sc, In, Ca, and Mg with the balance zirconia (ZrO 2 ), hafnia (HfO 2 ), titania (TiO 2 ), or mixtures thereof. The second phases have a characteristic thickness (T 6 ) of less than 2.0 micrometers (μm). The spacing between second phases has a characteristic thickness (T 5 ) of less than 8.0 micrometers (μm).

BACKGROUND

The disclosure relates to thermal barrier coating systems. Moreparticularly, the disclosure relates to thermal barrier coating systemsfor gas turbine.

U.S. Pat. No. 7,785,722 (the '722 patent) discloses a thermal barriercoating system comprising a YSZ base layer. Thereatop there may beseveral alternating layers of a molten silicate resistant material andYSZ. The molten silicate resistant material may comprise an oxide of alanthanide.

SUMMARY

One aspect of the disclosure involves an article comprising a thermalbarrier coating system atop a three-dimensional substrate. The thermalbarrier coating system comprises a matrix of a first chemistry withmultiple embedded second phases of a second chemistry. The matrixcomprises a stabilized zirconia. The second regions comprise at least 40mole percent of oxides having the formula Ln₂O₃, where Ln is selectedfrom the lanthanides La through Lu, Y, Sc, In, Ca, and Mg with thebalance zirconia (ZrO₂), hafnia (HfO₂), titania (TiO₂), or mixturesthereof. The second phases have a characteristic thickness (T₆) of lessthan 2.0 micrometers (μm). The spacing between second phases has acharacteristic thickness (T₅) of less than 8.0 micrometers (μm).

In additional or alternative embodiments of any of the foregoingembodiments: the matrix comprises a yttria stabilized zirconia; and thesecond phases comprise at least 40 mole percent of oxides having theformula Ln₂O₃, where Ln is selected from the lanthanides La through Lu,Y, Sc, In, Ca, and Mg with the balance zirconia (ZrO2), hafnia (HfO2),titania (TiO2), or mixtures thereof.

In additional or alternative embodiments of any of the foregoingembodiments: the second phases have characteristic thickness (T₆) of0.15-1.0 μm; and a ratio of the second phases characteristic thickness(T₆) to the spacing (T₅) between second phases, thickness-wise, isbetween 1:3 and 1:4.

In additional or alternative embodiments of any of the foregoingembodiments: the matrix with embedded second phases form a layer havinga thickness (T₄) of at least 76 micrometers.

In additional or alternative embodiments of any of the foregoingembodiments: the matrix with embedded second phases form a layer havinga thickness (T₄) of 76-350 micrometers.

In additional or alternative embodiments of any of the foregoingembodiments, the article further comprises: a bondcoat; and a first TBClayer between the bondcoat and the matrix.

In additional or alternative embodiments of any of the foregoingembodiments: the first layer has a nominal composition differing from acomposition of the matrix by the presence of one or more additives in atotal amount of up to 1.0 weight percent.

In additional or alternative embodiments of any of the foregoingembodiments: the characteristic thickness (T₆) of the second phases is0.15-1.0 micrometers (μm), and the characteristic thickness (T₅) of thespacing between second phases is 0.5-3.0 micrometers (μm).

In additional or alternative embodiments of any of the foregoingembodiments, the article further comprises: an additional coating layerwith a homogeneous chemistry atop the matrix with embedded secondphases.

In additional or alternative embodiments of any of the foregoingembodiments: the additional coating layer is more resistant to attack bymolten silicate deposits than is the matrix.

In additional or alternative embodiments of any of the foregoingembodiments, the article further comprises: an additional coating layeratop the matrix and comprising oxyapatite and/or garnet.

In additional or alternative embodiments of any of the foregoingembodiments: the matrix and second phases are in a layer of the thermalbarrier coating system with thickness (T₄) wherein the second phasesaccount for 5-20% of said layer by volume.

Another aspect of the disclosure involves an article comprising: asubstrate; and a thermal barrier coating system atop the substrate andhaving a matrix having a first chemistry and a plurality of embeddedsecond phases layered within the matrix having a second chemistry,different from the first chemistry, wherein the embedded second phaseswithin the matrix have a characteristic perimeter extent of 30-85%.

In additional or alternative embodiments of any of the foregoingembodiments: the matrix comprises a yttria stabilized zirconia; and thesecond phases comprise at least 40 mole percent of oxides having theformula Ln₂O₃, where Ln is selected from the lanthanides La through Lu,Y, Sc, In, Ca, and Mg with the balance zirconia (ZrO2), hafnia (HfO2),titania (TiO2), or mixtures thereof.

In additional or alternative embodiments of any of the foregoingembodiments: at a given location, a depthwise number of the embeddedsecond regions is 7-84.

Another aspect of the disclosure involves a process for coating asubstrate, the process comprising: generating a plume of depositionmaterial from a first source and a second source; alternating thecomposition of the plume by generating vapor from the first and secondsources in an alternating manner; and moving the substrate relative tothe first and second sources, wherein the moving of the substrate movesa given region of the substrate through the plume at a cyclic ratehaving a period greater than a duration of generation of the vapor plumefrom the second source.

In additional or alternative embodiments of any of the foregoingembodiments: the moving consists of a rotation.

In additional or alternative embodiments of any of the foregoingembodiments: a duration of generation of the vapor plume from the firstsource is 400-5000% of said period; and the duration of generation ofthe vapor plume from the second source is 30-99% of said period.

In additional or alternative embodiments of any of the foregoingembodiments: the first source comprises a yttria stabilized zirconia;and the second source comprises at least 40 mole percent of oxideshaving the formula Ln₂O₃, where Ln is selected from the lanthanide Lathrough Lu, Y, Sc, In, Ca, and Mg.

In additional or alternative embodiments of any of the foregoingembodiments: the first source comprises a yttria stabilized zirconia;and the second source comprises at least 40 mole percent of oxideshaving the formula Ln₂O₃, where Ln is selected from the lanthanide Lathrough Lu, Y, Sc, In, Ca, and Mg with the balance zirconia (ZrO2),hafnia (HfO2), titania (TiO2), or mixtures thereof.

In additional or alternative embodiments of any of the foregoingembodiments: the relative speed of the moving and the frequency ofalternation of the composition of the vapor plume are effective todeposit a matrix with embedded second phase patches of the coating fromthe first source and second source, respectively.

In additional or alternative embodiments of any of the foregoingembodiments: each of the second phase patches represents less than 85%of the surface area of the substrate.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional schematic view of a coatedsubstrate with various layers of exaggerated thickness to variousdegrees.

FIG. 2 is a partially schematic view of a first coating system in afirst deposition condition.

FIG. 3 is a view of the first coating system in a second depositioncondition.

FIG. 4 is a view of the first coating system in a third depositioncondition.

FIG. 5 is a view of the first coating system in a fourth depositioncondition.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

FIG. 1 schematically shows a coated part 20 comprising a metallicsubstrate 22 and a thermal barrier coating system 24 atop the surface 26of the substrate. After any surface preparation of the substrate, aninitial deposited layer 28 of the coating system is a bondcoat.Exemplary bondcoat is an MCrAlY, where M refers to a metal, typically Niand/or Co. An alternate bondcoat is a diffusion aluminide. Exemplarybondcoat deposition is via low pressure plasma spray (LPPS), highvelocity oxy-fuel (HVOF), air plasma spray (APS), cathodic arcdeposition, plating, and the like. The bondcoat has a thickness T₁. Theexemplary as-deposited bondcoat thickness may be reduced via growth of athermally grown oxide 30 which may grow during subsequent stages ofdeposition and is shown having a thickness T₂. Exemplary T₁ as appliedis 0.3-9 mil (7.6-229 μm), more narrowly 0.5-7 mil (13-178 μm). Thebondcoat may also diffuse with the substrate creating a diffusion regionor zone 32.

A multi-layer ceramic thermal barrier coating (TBC) 34 may be appliedafter bondcoat application. The exemplary TBC 34 comprises a base layer36 applied to a thickness T₃. The exemplary base layer is 7YSZ. Morebroadly, it may be a YSZ such as a 3-9% yttria with balance zirconia.Exemplary T₃ is 0.1-5 mil (2.5-127 μm), more narrowly, 0.5-3.5 mil(12.7-89 μm).

Atop the base layer 36, the TBC 34 includes a layer 38 having athickness T₄ and comprising a matrix 40 and embedded second phases 42.FIG. 1 is not drawn to scale. Specifically, the illustrated coatingthickness is extremely exaggerated relative to the substrate size forthe sake of clarity. The illustrated coating thickness variation aroundthe part is not realistic. Also, the illustrated thicknesses of theembedded second phases are also exaggerated for clarity. Also, thenumber of illustrated embedded second layers is lower than likely.

The matrix 40 has a first chemistry and the embedded second phases 42have a second chemistry, different from the first chemistry. Thebondcoat layer 28 and the base layer 36 are essentially continuous andof essentially constant thickness over the relevant area of thesubstrate (e.g., allowing for variations in substrate geometry and forintended differences in thicknesses (e.g., tapering toward near zero ata trailing edge of an airfoil so as to limit aerodynamic losses).Alternatively, with a combustor panel, a relatively uniform thicknessalong a hot side of the combustor panel but less or no thickness along acold side of a combustor panel.

The embedded second phases 42 may form incomplete layers that do notextend all the way around the three-dimensional substrate, such thatthey are embedded within the matrix 40. This is shown in FIG. 1.

Exemplary characteristic thickness T₆ of the embedded second phases 42are measured via an appropriate average (mean, medial, mode, optionallyweighted by the amount of material at such thickness). Alternatively, T₆may be a maximum measurement averaged among the regions of a given type.In general, similar thickness numbers may be used as these differentdefinitions may be expected to account for variations of about a factorof two or less. Exemplary T₆ is 0.1-2.0 μm, more narrowly, 0.15-1.0 μmor 0.2-0.8 μm.

Exemplary characteristic thicknesses T₅ of the matrix 40 between secondphases 42 are measured via an appropriate average (mean, medial, mode,optionally weighted by the amount of material at such thickness).Alternatively, T₅ may be a maximum measurement averaged among theregions of a given type. In general, similar thickness numbers may beused as these different definitions may be expected to account forvariations of about a factor of two or less. Exemplary T₅ is 0.3-8.0 μm,more narrowly, 0.5-5.0 μm or 1.0-3.0 μm.

Exemplary T₄ is 5-700 μm, more narrowly, 20-600 μm or 50-500 μm.

Exemplary T₃ is 3-125 μm, more narrowly, 5-100 μm or 12-75 μm.

As discussed below, the extent to which each individual exemplaryembedded phase 42 would extend around the part in the plane of the pagewould depend on the proportion of a single rotation period during whichdeposition of the coating chemistry corresponding to that instance ofembedded phase 42 was allowed. Exemplary proportions of the substratesurface area that each of the embedded phases 42 would cover would rangefrom 30% to 99%, more narrowly, 30-85% or 50% to 85%. Thus, withvariations depending on substrate geometry, viewed about an axis ofrotation during coating, the embedded faces 42 would cover suchpercentages of the perimeter of the part (e.g., exact correspondence ifcylindrical). In an alternative definition, such percent extents aremeasured between boundaries of the phases 42 where each such phasediminishes to 5 percent of its mean thickness.

At a given location along the coated substrate, the depthwise number ofsecond phases 42 may be at least two, more narrowly, at least four or atleast ten. Relative to the thickness T₄, the number of second phases 42at a given depthwise location may increase with T₄. With lowest T₄ of upto 3.0 mil (76 μm), an exemplary number is 1-12, more narrowly, 2-12 or2-7. At an exemplary T₄ of 21.0 mil (533 μm), the exemplary range wouldbe 7-84, more narrowly, 14-49. Thus, the upper limits of these ranges at3.0 and 21.0 mil may define an upper boundary of a linear functiondepending upon 1 ₄ and the lower boundaries may form a lower linearlimit.

There may be further variations. For example, there may be additionallayers such as a topcoat 50 (discussed below). Overall, and even withsuch exemplary additional layers, the thickness T₄ of the layer 38 mayrepresent at least an exemplary 30% of a total coating thickness, morenarrowly, 50-90%.

In an exemplary implementation, the matrix 40 may have a conventionalTBC composition such as a YSZ (e.g., 3-9 weight percent YSZ, or, inparticular, 7YSZ) which may be the same as the composition of the baselayer 36. Among possible candidate situations for differences betweenthe base layer 36 and the matrix 40 is the use of a luminescent dopantin the base layer. An exemplary dopant is a lanthanide. A laser may beused to excite luminescence from the dopped layer. The luminescence iscaptured by fiber optics and analyzed. Resulting information can be usedfor health monitoring of the TBC. Among candidate lanthanides are Eu andEr (because their luminescence wavelengths are in ranges that TBCs donot absorb and the luminescent lifetimes are long enough at hightemperatures to get a good signal to noise ratio). Other possibleadditives are Ti and/or Ta in small amounts to increase the toughness ofthe base layer. Although small variations between the composition of thelayers 40 and the base layer 36 may be desirable from performanceaspects, ease of manufacturing and using a common deposition materialsource may suggest using the same composition or a composition differingonly in contamination from materials of the embedded second phases.

The embedded second phases 42 may consist of a material having asignificantly lower mechanical strength and fracture toughness than thematerial of the matrix 40. Any in-plane stresses that exceed thestrength of the weak phases 42 (typically 50 to 200 ksi (345-1379 MPa)or 75-150 ksi (517-1034 MPa)) or in-plane strain energy that exceeds thefracture toughness of phases 42 (typically 1-5 J/m²) would be expectedto form cracks within phases 42 that would relieve stresses anddissipate strain energy. The associated interembedding of phases 42within the matrix 40 ensures that any cracks forming in phases 42 wouldbe contained within those phases—thereby avoiding linking of cracks thatmight lead to large spalls. The fact that the thickness T₆ of phases 42is intentionally kept small would ensure that crack would not widen asthey grow, ensuring both crack bridging and friction in the crack wake(both of which would promote dissipation of any strain energy built upin the coating).

Exemplary second phase 42 material may comprise an oxide of a lanthanideor similar material (e.g., material selected from the group consistingof the lanthanides La through Lu (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,Dy, Ho, Er, Tm, Yb, and Lu), Y, Sc, In, Ca, and Mg). More specifically,the second phase material may comprise a combination of such oxide andzirconia (ZrO₂), hafnia (HfO₂), titania (TiO₂), or mixtures thereof. Forexample, the second phase material may comprise 40-100 mole percent(more narrowly, at least 70 mole percent or 70-99 mole percent) of suchoxide. The oxide may be a mixture of such oxides or a single such oxide.One particular example involves gadolinia as said oxide in aconcentration of at least 90%, more particularly, essentially 100%(e.g., with only impurity levels of other components that do not affectperformance).

In the exemplary implementation, the second phases may account for5-15%, more narrowly, 10-13% of the volume of the layer 38 with thematrix 40 accounting for the remainder (ignoring porosity andtransitions). In the exemplary combination system, the presence of thebase layer 36 provides maximum mechanical strength in the area of thecoating where stresses in the coating are maximum.

Coating deposition may be via an otherwise conventional process andapparatus (e.g., EB-PVD or IE-EB-PVD) for depositing coatings such asYSZ and GSZ. An exemplary such system 100 (FIG. 2) comprises adeposition chamber 102 having an interior 104. In this example, thebondcoat has already been deposited (e.g., using anothersystem/chamber). A substrate/part holder 106 may hold the substrate(s)and may be driven by an actuator 108 for rotating the part (e.g., with aperiod of 2-20 seconds) and/or engaging in more complex manipulations asis discussed below.

A deposition material source comprises two distinct sources (subsourcesof the matrix 40 and second phases 42). A first source for the matrix 40comprises an ingot 122 (e.g., of 7YSZ or of slightly altered chemistryso as to yield a 7YSZ layer when subject to attrition of individualcomponents in the vapor cloud/plume). A second source associated withthe second phases 42 comprises a second ingot 124. One or more electronguns 126 may be positioned to direct electron beams 128 to exposedsurfaces of the ingots to maintain melt pools for generating the vaporcloud 140. The ingots may be contained in respective crucibles 132 and134.

FIG. 2 schematically shows a stage or mode wherein the electron beam isdirected to essentially exclusively vaporize material from the firstingot 122. This may be used for the deposition of the base layer 36. Inthis mode and associated stage(s), the vapor cloud 140 consistsessentially of material from the first ingot 122. Material from thesecond ingot 124 may be physically blocked from reaching the substrateby positioning an optional shutter 146 (actuator not shown) between thecrucible and the substrate. An exemplary elapsed time during thestage/condition/mode depicted in FIG. 2 would be between 500% and 2000%(5×-20×) of the time period to complete one rotation of thethree-dimensional substrate (more broadly, 400-5000%). This allows forthe formation of the base layer 36 around the entirety of the coatedportion of the part. Where different material or other properties arepresent in the base layer 36 versus the matrix 40, this step/stage or asimilar step/stage may be used to initially deposit an initial portionof the matrix 40.

Next, there may be a small compositional transition in the depositionprocess. For example, FIG. 3 shows the beam 128 reoriented and directedto the second ingot 124. Initially, the vapor cloud/plume will comprisea residual portion 142 from the first ingot and a portion 144 from thesecond ingot.

FIG. 4 shows the subsequent stage/mode wherein the beam remains directedto the second ingot 124 and the portion 142 has been expended so thatthe vapor cloud is essentially derived from the second ingot and not thefirst ingot so as to deposit the phases 42. Material from the firstingot 122 may be physically blocked from reaching the substrate bypositioning an optional shutter 148 (actuator not shown) between thecrucible and the substrate. The transition in the vapor depositionprocess depicted in FIG. 3 would be minimized by rapidly moving theshutter 148 into position immediately as the electron beam is moved fromfirst ingot 122 to second ingot 124.

Because, as described above, the phases 42 are very thin, the elapsedtime during the stage/condition/mode depicted in FIG. 4 would be muchless than that of the stage/condition/mode depicted in FIG. 2. Anexemplary elapsed time during the stage/condition/mode depicted in FIG.4 would be between 1% and 50% of the time period to complete onerotation of the three-dimensional substrate, or, more narrowly, between5% and 30% of that time period. Typical time periods to complete onerotation of three-dimensional substrates range from 2 to 20 seconds, ormore narrowly 3 to 15 seconds. This allows for the formation of thephases 42 as discrete regions rather than full layers around theentirety of the coated portion of the part.

From the stage/condition/mode depicted in FIG. 4, the system mayredirect the beam back to the first ingot (FIG. 5). In the FIG. 5condition/mode, initially the vapor cloud will comprise residualmaterial 144 from the second ingot and newly-vaporized portion 142 fromthe first ingot. As the portion 144 is eliminated by blockage by theshutter 146, the condition will revert back to the FIG. 2stage/condition/mode.

The cycle between depositions from the respective ingots (along with theoptional transition stages) may continue until the desired thickness ofcoating is deposited on the substrate.

An additional coating layer 50 (topcoat, e.g., with a homogeneouschemistry throughout it) may be deposited on top of the matrix 40 withembedded phases 42. The primary role of this topcoat would be to provideresistance to attack by molten silicate deposits that form on thecoatings during engine use due to ingestion of dirt. These deposits arecommonly referred to as CMAS (for calcium magnesium aluminosilicate).The additional coating layer broadly comprises a layer of oxyapatiteand/or garnet.

Herein, garnet refers broadly to an oxide with the ideal formula ofA₃B₂X₃O₁₂, where A comprises at least one of the metals selected fromthe group consisting of Ca, Gd, In, Mg, Na, K, Fe, La, Ce, Pr, Nd, Pm,Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Y, Ti, Zr, Hf, V, Ta, Cr, W,Mn, Tc, Re, Fe, Os, Co, Ir, Ni, Zn, and Cd; where B comprises at leastone of the metals selected from the group consisting of Zr, Hf, Gd, Al,Fe, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, In, Sc,Y, Cr, Sc, V, Nb, Cr, Mo, W, Mn, Fe, Ru, Co, Rh, Ir, Ni, and Au; where Xcomprises at least one of the metals selected from the group consistingof Si, Ti, Al, Fe, Cr, Sc, Y, V, Nb, Cr, Mo, W, Mn, Fe, Ru, Co, Rh, Ir,Ni, and Au; and where O is oxygen. Furthermore, limited substitution ofS, F, Cl, and OH for oxygen in the above formula is possible in thiscompound as well, with a concomitant change in the numbers of A, B, andX type elements in the ideal formula, to maintain charge neutrality.

Herein, oxyapatite refers broadly to A₄B₆X₆O₂₆ (II) where A comprises atleast one of the metals selected from the group consisting of Ca, Mg,Fe, Na, K, Gd, Zr, Hf, Y, Sc, In, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,Dy, Ho, Er, Tm, Yb, Lu, Sc, Y, Ti, Zr, Hf, V, Ta, Cr, W, Mn, Tc, Re, Fe,Os, Co, Ir, Ni, Zn, and Cd; where B comprises at least one of the metalsselected from the group consisting of Gd, Y, Sc, In, Zr, Hf, Cr, Sc, Y,V, Nb, Cr, Mo, W, Mn, Fe, Ru, Co, Rh, Ir, Ni, and Au; where X comprisesat least one of the metals selected from the group consisting of Si, Ti,Al, Cr, Sc, Y, V, Nb, Cr, Mo, W, Mn, Fe, Ru, C, Rh, Ir, Ni, and Au; andwhere O is oxygen. Furthermore, limited substitution of S, F, Cl, and OHfor oxygen in the above formula is possible in this compound as well,with a concomitant change in the numbers of A, B, and X type elements inthe ideal formula, to maintain charge neutrality.

As noted above, the coating system and deposition apparatus may beimplemented as a modification of an existing coating system andapparatus. The modification may be as simple as merely reprogramming theexisting controller of an existing apparatus already used to deposit atwo-component TBC (e.g., such as that of the '722 patent). Thereprogramming may merely alter the timing of the transitions betweendeposition stages. Other modifications may involve adding the secondsource to an existing single-source apparatus.

One or more embodiments have been described. Nevertheless, it will beunderstood that various modifications may be made. For example, whenapplied in the reengineering of an existing component and its coatingsystem, details of the existing component and coating system mayinfluence details of any particular implementation. Accordingly, otherembodiments are within the scope of the following claims.

1. An article comprising: a substrate; and a thermal barrier coatingsystem atop the substrate and having a matrix having a first chemistryand a plurality of embedded second phases layered within the matrixhaving a second chemistry, different from the first chemistry, wherein:the matrix comprises a stabilized zirconia; the second phases compriseat least 40 mole percent of oxides having the formula Ln₂O₃, where Ln isselected from the lanthanides La through Lu, Y, Sc, In, Ca, and Mg withthe balance zirconia (ZrO₂), hafnia (HfO₂), titania (TiO₂), or mixturesthereof; the second phases have a characteristic thickness (T₆) of lessthan 2.0 micrometers (μm); and the spacing between second phases has acharacteristic thickness (T₅) of less than 8.0 micrometers (μm).
 2. Thearticle of claim 1 wherein: the matrix comprises a yttria stabilizedzirconia; and the second phases comprise at least 40 mole percent ofoxides having the formula Ln₂O₃, where Ln is selected from thelanthanides La through Lu, Y, Sc, In, Ca, and Mg with the balancezirconia (ZrO₂), hafnia (HfO₂), titania (TiO₂), or mixtures thereof. 3.The article of claim 1 wherein: the second phases have characteristicthickness (T₆) of 0.15-1.0 μm; and a ratio of the second phasescharacteristic thickness (T₆) to the spacing (T₅) between second phases,thickness-wise, is between 1:3 and 1:4.
 4. The article of claim 1wherein: the matrix with embedded second phases form a layer having athickness (T₄) of at least 76 micrometers.
 5. The article of claim 1wherein: the matrix with embedded second phases form a layer having athickness (T₄) of 76-350 micrometers.
 6. The article of claim 1, furthercomprising: a bondcoat; and a first TBC layer between the bondcoat andthe matrix.
 7. The article of claim 6, wherein: the first layer has anominal composition differing from a composition of the matrix by thepresence of one or more additives in a total amount of up to 1.0 weightpercent.
 8. The article of claim 1 wherein: the characteristic thickness(T₆) of the second phases is 0.15-1.0 micrometers (μm), and thecharacteristic thickness (T₅) of the spacing between second phases is0.5-3.0 micrometers (μm).
 9. The article of claim 1, further comprising:an additional coating layer with a homogeneous chemistry atop the matrixwith embedded second phases.
 10. The article of claim 9 wherein: theadditional coating layer is more resistant to attack by molten silicatedeposits than is the matrix.
 11. The article of claim 6, furthercomprising: an additional coating layer atop the matrix and comprisingoxyapatite and/or garnet.
 12. The article of claim 1, wherein: thematrix and second phases are in a layer of the thermal barrier coatingsystem with thickness (T₄) wherein the second phases account for 5-20%of said layer by volume.
 13. An article comprising: a substrate; and athermal barrier coating system atop the substrate and having a matrixhaving a first chemistry and a plurality of embedded second phaseslayered within the matrix having a second chemistry, different from thefirst chemistry, wherein: the embedded second phases within the matrixhave a characteristic perimeter extent of 30-85%.
 14. The article ofclaim 13 wherein: the matrix comprises a yttria stabilized zirconia; andthe second phases comprise at least 40 mole percent of oxides having theformula Ln₂O₃, where Ln is selected from the lanthanides La through Lu,Y, Sc, In, Ca, and Mg with the balance zirconia (ZrO₂), hafnia (HfO₂),titania (TiO₂), or mixtures thereof.
 15. The article of claim 13wherein: at a given location, a depthwise number of the embedded secondregions is 7-84.
 16. A process for coating a substrate, the processcomprising: generating a plume of deposition material from a firstsource and a second source; alternating the composition of the plume bygenerating vapor from the first and second sources in an alternatingmanner; and moving the substrate relative to the first and secondsources, wherein: the moving of the substrate moves a given region ofthe substrate through the plume at a cyclic rate having a period greaterthan a duration of generation of the vapor plume from the second source.17. The process of claim 16 wherein: the moving consists of a rotation.18. The process of claim 16 wherein: a duration of generation of thevapor plume from the first source is 400-5000% of said period; and theduration of generation of the vapor plume from the second source is30-99% of said period.
 19. The process of claim 16 wherein: the firstsource comprises a yttria stabilized zirconia; and the second sourcecomprises at least 40 mole percent of oxides having the formula Ln₂O₃,where Ln is selected from the lanthanide La through Lu, Y, Sc, In, Ca,and Mg.
 20. The process of claim 16 wherein: the first source comprisesa yttria stabilized zirconia; and the second source comprises at least40 mole percent of oxides having the formula Ln₂O₃, where Ln is selectedfrom the lanthanide La through Lu, Y, Sc, In, Ca, and Mg with thebalance zirconia (ZrO₂), hafnia (HfO₂), titania (TiO₂), or mixturesthereof.
 21. The process of claim 16 wherein: the relative speed of themoving and the frequency of alternation of the composition of the vaporplume are effective to deposit a matrix with embedded second phasepatches of the coating from the first source and second source,respectively.
 22. The process of claim 21 wherein: each of the secondphase patches represents less than 85% of the surface area of thesubstrate.